1. Field of the Invention
The present invention relates to an oil separator for separating the oil mist from gaseous fluids, such as a blowby gas, and in particular, to an oil separator which is suitably used in a gas engine for a gas heat pump type air conditioner.
2. Description of the Related Art
An air conditioner, in which a heat pump is used for cooling and heating operations, is provided with a refrigerant circuit comprising an indoor heat exchange apparatus, a compressor, an outdoor heat exchange apparatus, an expansion valve, etc. When the refrigerant circulates in the refrigerant circuit and exchanges heat with air in the indoor heat exchange apparatus and the outdoor heat exchange apparatus, the air conditioned chamber is heated or cooled. In addition, in order to heat the chamber, not only the outdoor heat exchange apparatus but also a refrigerant heating apparatus for heating the refrigerant directly is sometimes provided in the refrigerant circuit.
In recent years, an air conditioner has been suggested, which comprises a gas engine, instead of an ordinary motor, as a driving source for the compressor provided in the refrigerant circuit. An air conditioner utilizing a gas engine is called a gas heat pump type air conditioner (abbreviated as xe2x80x9cGHPxe2x80x9d below). The GHP can use gas, which is relatively cheap, as fuel; therefore, the running cost thereof can be reduced, compared with an air conditioner comprising a compressor driven by the ordinary motor (abbreviated as xe2x80x9cEHPxe2x80x9d below).
Moreover, in the GHP, when waste heat of gas at a high temperature discharged from the gas engine during the heating operation is used as the heat source for the refrigerant, the heating ability can be improved, and the use efficiency of energy can also be improved. In addition, when the waste heat of the gas discharged from the gas engine is used in the GHP, the GHP does not require a special device, such as the refrigerant heating device explained above.
Furthermore, the GHP can utilize the engine waste heat to defrost the outdoor heat exchange apparatus during the heating operation. In general, the EHP defrosts the outdoor heat exchange apparatus by stopping the heating operation and temporarily performing the cooling operation. That is, when the EHP defrosts, cooled air is introduced into the chamber. Therefore, a person in the chamber feels unpleasant. In contrast, the GHP can utilize the waste heat, and it can continuously perform the heating operation without such the problem which is caused by the EHP.
The GHP has many advantages as explained above; however, it also has the following problems.
As explained above, the GHP uses the gas engine as a driving source for the compressor. In the gas engine, oil contained in the blowby gas may rise to problems. The blowby gas is gas which leaks from the combustion chamber into a crank case through a gap between the piston ring and the cylinder. In general, the blowby gas is returned from the crank case into an engine intake system and is then sent to the combustion chamber again.
Since the blowby gas contains a lubricating oil in a the state of a mist (abbreviated as xe2x80x9coil mistxe2x80x9d below), at a suitable positions on a line for the flow of the blowby gas (abbreviated as xe2x80x9cblowby gas linexe2x80x9d below), oil separators for accumulating and removing the oil mist, such as a blowby gas filter, are provided.
FIGS. 11, 12A, and 12B show a conventional oil separator which is used as a blowby gas filter. In the figures, reference number 140 denotes an oil separator, 141 denotes a case body, 142 denotes a lid, 143 denotes a filter, 144 denotes gaseous fluid entrance, 145 denotes a gaseous fluid exit, and 146 denotes an outflow exit for the oil mist accumulated by the filter 143. Moreover, the case body 141 and the lid 142 comprise the casing of the oil separator 140.
In the oil separator 140, the blowby gas, which flows in through the entrance 144 connected to the crank case of the gas engine, passes through the filter 143 and is sucked through the exit 145 by the intake system of the gas engine. The oil mist contained in the blowby gas is separated and removed as it passes through the filter 143, falls to the bottom of the case body 141, and is then returned to the oil pan of the gas engine through the outflow exit 146. In the oil separator 140, in order to improve the separation efficiency of the oil mist, the height of the filter 143, through which the blowby gas passes, is increased as much as possible. It is necessary to replace the filter 143 after a given operation time of the oil separator 140. Therefore, in order to change the filter 143, the lid 142 can detach from the case body 141. In addition, in order to easily change the filter 143, the lid 142 is attached at the side of the case body 141, where an opening having the largest area can be formed.
However, if the lid 142 is formed at the side of the case body 141, there is the possibility that the oil falling to the bottom of the case body 141 will leak from a gap between the case body 141 and the lid 142. In particular, when the oil mist contained in the blowby gas is separated and removed in the oil separator 140, the pressure at the bottom of the case body 141 where the outflow exit 146 is provided is greater than the atmospheric pressure at the outside of the case body 141. That is, the pressure at the bottom of the case body 141 where the outflow exit 146 is provided in a positive pressure region. Therefore, there may be oil leak due to the pressure difference, at any gap occurring at the contact portion.
An oil leakage can be solved by improving the seal between the case body 141 and the lid 142. However, in order to obtain a good seal, the structure of the contact portion must be complicated; therefore, a cost for manufacturing the oil separator will increase. In addition, since the case body 141 and the lid 142 are made of synthetic resins, if the structure thereof is complicated, their formability may be decreased.
In addition, in the conventional oil separator 140, since the filter 143 is made of nonwoven fabrics, which have inferior shape maintaining properties, there is the problem that a gap S can easily occur between the filter 143 and the inside wall of the case body 141, as shown in FIG. 12A. If the gap S is generated, the blowby gas containing the oil mist passes through the gap S and flows out through the exit 145, without passing through the filter 143. The gap S decreases the separation efficiency of the oil mist in the oil separator 140. Therefore, it is desired for the blowby gas to pass with certainty through the filter 143. In addition, in the conventional oil separator 140, since the separation of the oil mist is carried out by only the filter 143, there is the problem that it is difficult to obtain a sufficient separation efficiency. In this case, the separation efficiency can be improved by increasing the thickness of the filter 143. However, an increase in the thickness of the filter 143 causes a significant pressure loss. Therefore, the separation efficiency cannot be sufficiently improved only by increasing the thickness of the filter 143. In the light of the above, it is desired to provide oil separator in which the oil mist contained in the blowby gas can be efficiently separated without increasing the pressure loss.
Therefore, one of objects of the present invention is to improve the performances of the oil separator for removing the oil mist from the gaseous fluids, such as the blowby gas. In particular, an object of the present invention is to provide an oil separator which can be manufactured at a low cost and can prevent the leakage of removed oil, and an oil separator which has improved separation efficiency of the oil mist contained in the gaseous fluids without increasing the pressure loss.
In order to achieve the object, the present invention provides an oil separator for separating oil from a gaseous fluid containing oil in the state of a mist comprising: a hollow case body comprising an opening at the top thereof; a lid for covering the opening formed at the case body; and a filter in the case body; wherein an entrance for flowing of the gaseous fluid into the case body is formed at the lower side of the case body, an exit for outward flow of the gaseous fluid is formed at the lid, and an outflow exit for outward flow of oil which has been separated is formed at the bottom of the case body.
In the oil separator, since the opening, which is formed at the top of the case body, is covered with the lid, the case body and the lid do not come into contact with each other at the bottom of the case body, i.e., at the portion to which the separated oil descends. Therefore, it is possible to flow out with certainty the separated and removed oil from the oil separator without oil leaks at the contact portion between the case body and the lid. In addition, the separator has a simple structure and it can be manufactured at a low cost.
In the oil separator, it is preferable to provide a guide for introducing the gaseous fluid flowing from the entrance to the exit into the center of the filter.
In the oil separator, since the gaseous fluid is introduced into the center of the filter by the guide, the amount of the gaseous fluid which does not pass through the filter can be significantly decreased. If there is a gap between the filter and the inside wall of the case body, it is possible to improve the separation efficiency of the oil mist.
In the oil separator, it is preferable for the guide to be a cylindrical member provided at the bottom surface of the lid so as to protrude toward the inside of the case body, or to be a plate ring member provided at the inside wall of the case body above the entrance so as to protrude toward the inside of the case body.
In addition, in the oil separator, it is preferable for the case body to comprise a large upper portion in which the filter is placed and a small lower portion in which the entrance and the outflow exit are provided, and for the gaseous fluid flowing from the entrance to the exit to be introduced into the center of the filter at a connection portion between the large upper portion and the small lower portion.
In the oil separator, since the connection portion between the large upper portion and the small lower portion acts as a guide for introducing the gaseous fluid into the center of the filter, if there is the gap between the filter and the case body and the lid, it is possible to improve the separation efficiency of the oil mist.
In the oil separator, it is preferable for the gaseous fluid entrance and the outflow exit for the separated oil to be formed in a positive pressure region, and for the gaseous fluid exit to be formed in a negative pressure region.
If the gaseous fluid is a blowby gas for an internal combustion engine, the positive pressure region is connected to the crank case of the internal combustion engine, and the negative pressure region is connected to the intake system of the internal combustion engine. Therefore, in the oil separator, since the contact portion between the case body and the lid is formed in a negative pressure region, that is, the pressure at the connection portion is lower than the pressure outside of the case body, i.e., lower than the atmospheric pressure, the oil is less likely to leak from the oil separator.
In addition, if the oil separator is used to remove the oil mist from the blowby gas of the internal combustion engine, since the gaseous fluid exit is connected to the intake system, it is possible to easily form a negative pressure region.
In order to achieve the object, the present invention provides another oil separator for separating oil from a gaseous fluid containing oil in the state of a mist comprising: a circular flow formation portion for generating a circular flow of the gaseous fluid introduced in the casing and a filter portion in which the circular flow of the gaseous fluid passes.
In the oil separator, the oil mist is separated by the centrifugal force occurring due to the circular flow formation portion and by passing through the filter. In other words, the oil mist is separated from the gaseous fluid due to the effects provided by the circular flow formation portion and the filter. Therefore, it is possible to improve the separation efficiency without increasing the pressure loss.
In the oil separator, it is preferable to provide an entrance for inward flow of the gaseous fluid at the lower side of a casing, an exit for outward flow of the gaseous fluid at the top surface of the casing, an outflow exit for outward flow of the oil which has been separated is formed at the bottom of the casing, and the circular flow formation portion is provided at the lower portion of the casing.
In the oil separator, since the gaseous fluid passes through the circular flow formation portion and thereby the amount of the oil mist contained in the gaseous fluid decreases due to the centrifugal force, a gaseous fluid containing only a small amount of oil mist passes through the filter. In addition, the oil removed by the centrifugal force flows out the casing through the outflow exit without passing through the filter place portion. Therefore, it is possible to increase the operation life of the filter. In addition, oil separated and removed by the filter descends due to its own weight and flows out the casing through the outflow exit.
In addition, it is preferable for the position and the direction of the opening of the gaseous fluid entrance to be adjusted such that the gaseous fluid is introduced into the casing along the inside wall of the casing. As a result, it is easy for the gaseous fluid to form a circular flow.
In addition, it is also preferable to provide a circular flow formation guide for the gaseous fluid in the circular flow formation portion. This makes it easy to form a circular flow. Furthermore, it is also preferable for the gaseous fluid exit to be provided at the center of the top surface of the casing. This makes it possible to generate the circular flow of the gaseous fluid.
It is preferable for the gaseous fluid to be the blowby gas of the internal combustion engine, for the gaseous fluid entrance to be connected to the crank case of the internal combustion engine, and for the gaseous fluid exit to be connected to the intake system of the internal combustion engine. Due to this, since the gaseous fluid pushed out by the crank case at a positive pressure is taken into the intake system at a negative pressure through the oil separator, it is possible to generate a smooth flow of the gaseous fluid in the oil separator.